Tensile testing of optical fibers is commonly carried out to ensure that optical fibers have the desired tensile strength for their applications, and to ensure that there are not anomalies or defects in the fiber which may affect its integrity.
In one method of screening or proof-testing optical fiber, a length of optical fiber is isolated between two capstan assemblies, each capstan assembly having a capstan pulley and a capstan belt, and then a tensile stress is applied to the isolated length of optical fiber. The capstan belt is used to hold the fiber in place and prevent fiber slip on the capstan pulley as the tensile stress is applied. When screening spliced optical fibers, where the coating has been stripped to splice bare glass ends, and then the bare glass is recoated with a layer of coating, or recoat, the increased compressive stress from the belt may result in coating defects at or near the splice joint.
Another method previously disclosed includes the use of multiple wraps of optical fiber around a capstan to isolate the portion of the optical fiber being tensile tested.
In each of these methods, whether a belt is used or whether multiple wraps are used around the capstan, the optical fiber is tested in an intermittent fashion, by advancing the fiber a given length, isolating the portion of the fiber between the capstans, and then testing the tensile strength of the length of fiber between the first and second capstans. When attempting to use tensile testing devices as described above in a continuous tensile testing method, the optical fiber is likely to be subject to slippage on the capstan, increased wear on the optical fiber and its coating as a result of the belt compressing the optical fiber against the capstan, and tangling or “web-walking” about the capstan.